Due to human error, an LP Gas transport truck when loaded sometimes is pulled away from the bulk loading station without shutting off the service valve or disconnecting the filler hose. This, along with other mishaps in the loading area may cause rupture and damage to the hose that drops the pressure in the hose to atmospheric pressure and permits LP Gas to flow as liquid through the piping and vaporize inside the piping and hose and be released in the surrounding area. The hazards created of causing fires, destruction of property, personal injury and loss of fluid are great.
While fusible materials and springs have been used heretofore for initiating the closure of valves under dangerous circumstance, it is highly desirable that the manual control valve, as a single readily replaceable or serviceable unit, serve automatically as a shut-off dispensing valve as well as a flow control valve when a downstream conduit rupture develops whether the driver disconnects the hose first or drives away without valve shut-off and hose disconnection.